For over 150 years, speculation has been rampant as to what killed the crew of the H.L. Hunley, a 40-foot Confederate submarine, which sank off the coast of South Carolina on February 17, 1864.

The Huntley’s First Battle Was Also Its Last

The Hunley sunk a Union warship, the USSHousatonic, and was the first, and only, sub in Confederate history to do so. The enemy vessel was taken down with a rudimentary torpedo—a copper keg filled with 135 pounds of black powder attached to a pole 16 feet from the ship’s hull. The torpedo hit the Housatonic‘s hull below the waterline, causing a tremendous explosion. The warship sunk in just five minutes and landed upright in 30 feet of water. Five men died, and the remaining crew members were later rescued. The Hunley’s men should have been celebrating their wartime success, but the submarine never resurfaced, and the vessel disappeared without a trace.

130 Years Later The Hunley Is Found

Following the war, the Hunley was lost to history. It was believed the eight-man crew drowned, suffocated, or was shot by an errant seaman aboard the doomed Housatonic. The fate of the vessel was finally revealed 1995 when the sub was found 300 meters from the wreck of the Housatonic near Charleston Harbor. It was raised in 2000, and it has been under investigation by Clemson University scientists ever since.

When researchers opened the crew compartment of the Hunley, they soon realized that none of the prior theories held up. Their skeletons were all found at their stations, with all their bones intact and unbroken. The drain pumps were closed, as were the air hatches. The sub was surprisingly untouched, minus a hole in one conning tower and a broken window.

The Mystery Of The Hunley Is Solved

Duke University researcher, biomechanist, and Civil War buff Rachel Lance conducted an exhaustive, three-year investigation on the crew’s remains and the Hunley. She’s concluded that shockwaves from the torpedo explosion killed the men inside while causing minimal damage to the sub itself. The shockwave traveled through the soft tissues their bodies, and into their lungs and brains and killed them instantly. If they had survived the blast, they would’ve tried to release the keel ballast weights, start pumping water, or make an effort to escape the sub in some way, but nothing like that ever occurred.

A Pocket Watch Solidifies A Theory

Another piece of evidence stood in Lance’s favor. Crewmember Lt. George Dixon’s pocket watch had stopped at 8:23—about the time of the Hunley’s attack on the Housatonic. “It appears it didn’t wind down naturally,” according to a 2007 update by a research partnership known as the Hunley Project. “Something traumatic—perhaps water, a shock wave, or some other intervening force—caused it to stop at that precise time.”